Preparation of amines



Sept 12, 1944- W. o. POOL ETAL V PREPARATION OF AMI-NES i Filed June 10,194l` TRHP /J w an J 7H/WN :PHL VE INVENTORS POZS;

14Min/720 /DOo Patented Sept. 12, 1944 PATENT orrlcs f PREPARATION FANHNES william o. P001, chicago, and Ralph i1. nous,

La Grange, lll., assigner-s to Armour and Company, Chicago, Ill., acorporation of Illinois Application June 10, 1941, Serial No.l 397,418

SClaims. This invention relates to the hydrogenation of aliphatic.nitriles to produce the correspOnding amines, and deals particularlywith processes which are selective to the formation of secondary ratherthan primary amines.

The high molecular weight secondary amines are becoming of greatcommercial importance in many industrial elds, such as insecticides, theflotation of ores, and in many other commercial applications.

In the past there has been no satisfactory process known wherebysecondary amines could be obtained directly from the correspondingnitriles, except in admixture with amajor portion of primary amines. Inthe known processes for the hydrogenation of nitriles', invariably theproduct would be a mixture of primary, secondary and tertiary amines inwhich the primary amines were a very substantial constituent.

It is an important object of the invention to provide a processl fortreating nitriles with hydrogen which will yield a higher proportion ofsecondary amines. Another object is to provide y such a process which isunfavorable to primary amines as an end product and which can beadjusted to yield secondary or secondary and tertiary amines in greaterproportion. It is also desired that the reaction take lplace easilywithout the need for long holding periods.

We have discovered that secondary amines can be selectively 'produced'by conducting the reaction vof the nitriles with hydrogen in thepresence of a special catalyst which is produced by reducing the saltsof nickel or cobalt. We nd thatby using reduced nickel formate, forexample, there is a very pronounced effect favorable' to the formationof secondary amines. When such a catalyst is used the :nal amine productwill contain a much greater amount of secondary'and a much lesser'amount of primary amines than could be obtained when using othercatalysts, such as the Raney catalyst which is derived from an aluminumalloyof the nickel.

The reasons for this special effect of reduced organic salt catalysts inthe nitrile-hydrogen reaction is at present not well understood, and maybetter be dealt with after thefollowing detailed description of theimproved process.

One type of apparatus which may beused in practicing the invention isillustrated schematically in the accompanying drawing.

' will receive a suitable .heating uid for maintaining the tankand itscontents at a desired tem.

25 such metals.l

perature. An agitator I 2, which may be powered by an electric motor, orother suitable means, is provided for maintaining the tank contentsunder agitation during the treatment. A thermocouple designated I3serves for indicating the temperature being maintained.

A line I4 leads from the top portion of'tank I0 into a trap I5, and theline I6 leads from the trap back to the bottom of the tank. The line I1provided with valve I8 leads from the upper portion of the trap to theatmosphere. A gauge I9 is provided to indicate the pressure beingmaintained in the system.

In carrying out the improved process using the illustrated apparatus,the nitrile is mixed with a suitable quantity of the special catalyst inthe mixing tank and the mixture discharged through the valve equippedline 2| into the reaction tank I0. I f desired the mixing of 20 thecatalyst with the nitrile may be conducted in' the tank I0 itself. The-catalyst maybe a reduced salt of either nickel orcobalt, preferformatemakes a very superior Icatalyst.

With the mixture of nitrile and special catalyst in the tank I0 theheating fluid may then be admitted to the heating jacket and theagitator 1 started. When the reaction temperature has been reached,hydrogen is admitted under pressure through line 22. 'I'hough theinvention may be practiced at any temperature which will producereaction, we prefer to use a temperature of between '160 C. as a lowerlimit and labout 350 C., or as high as can -be had without causingobjectionable cracking, as the upper limit.

We nd that this range of temperatures is in the present process morefavorable to the pro- 40 duction of secondary and tertiary amin than arethe ordinary temperatures below this range..

Hydrogen should be introduced in amounts and under pressure suiiicientto replace the loss occasioned by venting or by being taken up in 45reaction so that there is a sufcient quantity present for furtherreaction.

During the treatment with hydrogen gas the resulting gases may escapethrough the line I4,'.

' and any entrained matter is caught in the trap I5 and so returned tothe system. The valve 23 Yserves to regulate the quantity of gases whichvare permitted to pass-oil. It is preferable that .l the gases be thusvented during the reaction, it

being understood that the desired pressure tor reaction is to bemaintained at the same time Of these the reduced nickel` been obtainedandduring the time the reactants reach the preferred temperature.

The nitriles used in forming secondary amines according to the improvedprocesses may be prepared, for example, by hydrolyzing oil, such as`cottonseed oil, or soya bean oil, to produce glycerine and mixed fattyacids, and then reacting the fatty acids with ammonia to produce thenitnes. advantageously thc acids obtainedV upon hydrolysis may befractionally distilled and a fraction having a desired boiling rangerecovered, this recovered fraction may then be subjected to reactionwith ammonia to form nitriles in accordance with the method herein setforth. suitably, the fatty acids themselves may be hydrogenated to formsaturated fatty acids before reaction with ammonia, and the hydrogenatednitriles so formed then subjected to the hydrogenated treatment hereinset forth to produce secondary amines. Any suitable method may bevemployed for producing the nitriles for use in this hydrogenationreaction.

The special catalysts employed in our invention may be prepared byreducing the metal salts with hydrogen gas. suitably, the nickel orcobalt salts are suspended in an oil, such as cottonseed oil, andhydrogen passed to the mixture while maintaining a temperature of about180 to 300 C. If nickel formate, for example, is the salt used, theresulting product of reduction contains and sub-oxides of nickel andminor quantities of other substances not now identified specitlcally.Likewise catalysts formed upon reduction of cobalt salts beforementioned contain free cobalt,

, the cobalt salt, cobalt oxides and sub-oxides and very eiective inproducing. secondary amines, butv vi'ree nickel, traces of nickelformate, also oxides hydrogen to produce the secondary amine prod-Example `I 114.3 g. cf crude stearcnitruc was hydrcgcnatcd uaing'oatsog. cr catalyst containing 0.1143 g.

of nickel prepared from nickel formate. The

Example II 114.3 g. of distilled stearcnitrile was hydrogenated using0.1920 g.v of catalyst containing 0.1143 g. of Raney nickel. The bombwas shaken at 220 C. for 100 minutes. The product consisted of Per centOctadecylamine 64.4 Dioctadecylamine 28.8 Unchanged nih-HP 6.8

As seen by comparing the foregoing examples,

the use of the reduced nickel formate catalyst produces a very markedselectivity favorable to secondary amines. A similar selectivity isobtained when using the reduced oxalate or acetate of nickel.v Thereduced nickel tartrate is also due to quite incomplete reduction of themetal salt, the nitrile-hydrogen reaction takes-place somewhat moreslowly. The other reduced nickel salts are also selective to secondaryamines. lWe

have 'also found that substantially the same selectivity is obtainedwhen the catalyst is prepared from a salt of cobalt.

While we` do not wish to bev bound by any theory which may be given inany attempt to explain the improved results obtained by the processesherein given, the following formulas may be helpfulinexplanation:

a-oNwmwR-c-N/ 1)` it \H tion Where two molecules unite to produce asecondary amine with ammonia being released'. In each of these equationsR represents an aliphatic radical which in most instances Will containsix or more carbon atoms. Another possibility is that the secondary andprimary amines combine to x f ormtertiaryamines according to thefollowing equation:

- Assuming that the reactionstaking place in the formation of secondaryand tertiary amines follow the lines of Equations I, II; and III abovegiven, it then appears that though the reaction of Equation I proceedsvery well under the in- 'bomb W33 shaken at 220, C- for 9 The 70 iuenceof the ordinary reduced nickel-aluminum productoonsistedof: catalyst,this catalyst may inhibit, cr at least Per Cent fail to promote thereaction component repre- Octdeylmne 233 sented by Equations l1 and III,While on the Dioctadecylamine 59.4 other 4hand the reaction componentsof Equations Unchanged nitrle -s 12.4 II and III are eiectively promotedunder the influence of the reduced metal salt catalyst oi' the presentinvention.

' 'Ihe foregoing description and examples have been given for purposesoi.' explanation only and no unnecessary limitation should be understoodtate, and nickel oxalate, while saidsalt is suspended in a'liquidorganic medium, to prepare a catalyst therefrom; and treating saidnitriles with hydrogen under conditions of elevated temperature andpressurein the presence of said catalyst to 'produce an amine mixturehaving a high proportion of secondary amines.

2. -A process as in claim 1 where said salt is nickel formate.

3. A process as in claim 1 where said salt is' nickel acetate.

- WILLIAM o. POOL.

RALPH H. PO'ITS.

